Practical limitations to selenium annealing of compound co-sputtered Cu2ZnSnS4 as a route to achieving sulfur-selenium graded solar cell absorbers

THIN SOLID FILMS

卷:623

Article

Ross, N.^1,2  Larsen, J.²  Grini, S.¹  Vines, L.¹  Platzer-Bjorkman, C.² 

[1] Univ Oslo, Ctr Mat Sci & Nanotechnol, Dept Phys, POB 1048 Blindern, N-0316 Oslo, Norway

[2] Uppsala Univ, Dept Engn Sci, Div Solid State Elect, Angstrom Lab, Box 534, SE-75121 Uppsala, Sweden

关键词: CZTSSe;    Diffusion;    Crystallisation;    Sodium;    Band gap gradient;   

DOI  :  10.1016/j.tsf.2016.12.044

来源: Elsevier

【 摘 要 】

The suitability of selenium annealing as a technique to introduce energy band gap gradients via sulfur selenium substitution in Cu2ZnSnS4 (CZTS) films is evaluated. Compound co-sputtered CZTS precursors are annealed in selenium atmosphere at 425 degrees C, either as-deposited or after a short time sulfur pre-anneal. The films are investigated by Raman spectroscopy and X-ray diffractometry, and the spatial distribution of elemental species measured by secondary ion mass spectrometry and energy dispersive X-ray spectroscopy. Sulfur-selenium gradients are not achieved for the as-deposited precursor. Sulfur-selenium gradients are achieved in the early stages of annealing for pre-anneal samples, where Cu2ZnSn(S,Se)(4) (CZTSSe) formation is found to be correlated spatially with sodium distribution. These gradients are lost as the annealing progresses. Selenisation occurs by CZTSSe grain growth, rather than by direct substitution of selenium for sulfur. The spatial correlation of high sodium concentration with CZTSSe formation suggests that liquid phase sodium selenide facilitates selenium incorporation during recrystallisation, limiting the practicality of anion-grading of CZTSSe during the annealing step as a means of establishing a graded band gap. (C) 2017 Elsevier B.V. All rights reserved.

【 授权许可】

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